scholarly journals Analysis of Open-Source CFD Tools for Simulating Complex Hydrodynamic Problems

2020 ◽  
Author(s):  
Mohd Atif Siddiqui ◽  
Hui-li Xu ◽  
Marilena Greco ◽  
Giuseppina Colicchio
Keyword(s):  
Free Surface ◽  
Open Source ◽  
Vortex Shedding ◽  
Cfd Simulation ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Sea Waves ◽  
Viscous Effects ◽  
First Case ◽  
Flow Effects

Abstract OpenFOAM (OF) represents an attractive and widely used open-source environment for simulating complex hydrodynamic scenarios with several implemented numerical methods and wide variety of problems it can be applied to. For commercial and open-source solvers, though, expertise and experience are required to get physical and reliable results. Here, without pretending to be exhaustive, we aim to contribute in highlighting advantages and challenges of some key computational fluid dynamics (CFD)-simulation tools, with focus on the OF platform. We examine the effect of grid type, grid size and time-evolution scheme. Dynamic-mesh techniques and their influence on local and global numerical results are discussed, as well as the use of an overset grid versus a deforming mesh. Lastly, possible error sources in CFD simulations are discussed. These numerical studies are performed investigating two complex hydrodynamic problems: 1. a fully-immersed flapping hydrofoil aimed to generate thrust, 2. a damaged and an intact ship section fixed in beam-sea waves, in forced heave and roll motion in calm water. In the first case, vortex-shedding and wake features are crucial; in the second case, free-surface flow effects play the key role while the importance of vortex-shedding and viscous-flow effects depends on the scenario. The first problem is solved with OF and validated with results from benchmark experiments. The second problem is solved using (A) OF, (B) an in-house CFD solver and (C) a fully-nonlinear potential-flow code. A and B assume laminar-flow conditions and use, respectively, a volume-of-fluid and a level-set technique to handle the free-surface evolution. C is considered to examine importance of nonlinear versus viscous effects for the examined problems. The results are compared against in-house experiments.

scholarly journals SPH Open Boundary Simulation of Free-Surface Flow Over Ogee-crested Spillway

2021 ◽  
Vol 28 (2) ◽  
pp. 137-151
Author(s):  
Rizgar Karim ◽  
Jowhar Mohammad
Keyword(s):  
Free Surface ◽  
Open Source ◽  
Water Surface ◽  
Surface Profile ◽  
Free Surface Flow ◽  
The United States ◽  
Surface Flow ◽  
Absolute Difference ◽  
Open Boundary ◽  
Water Surface Profile

This study was conducted to compare water surface profiles with standard ogeecrested spillways. Different methods were used, such as (experimental models, numerical models, and design nomographs for the United States Army Corps of Engineers, USACE). In accordance with the USACE specifications, three different models were constructed from rigid foam and then installed in a testing flume. The water surface profile has been recorded for these models with different design heads. For modeling the experimental model configurations, a numerical model based on the smoothed particle hydrodynamics (SPH) technique was used and is developed to simulate the water surface profile of the flow over the ogee-crested spillway. A 2D SPHysics open-source software has been used in this study, using the SPH formulation to model fluid flow, developing the SPH boundary procedure to handle open-boundary simulations, and modifying the open-source SPHysics code for this purpose. The maximum absolute difference between the measured and computed results of the water surface profile for all head ratios of (H/Hd), does not exceed 4.63% at the crest region, the numerical results for the water surface profile showed good agreement with the physical model results. The results obtained experimentally and numerically by SPH are compared with the CFD results in order to be more reassuring from the results. Additional comparisons were made using interpolated data from USACE, Waterways Experiment Station (WES), and design nomographs. The SPH technique is considered very promising and effective for free surface flow applications.

Adaptive Grid Refinement for Free-Surface Flow Simulations in Offshore Applications

2015 ◽  
Author(s):  
Peter van der Plas ◽  
Arthur E. P. Veldman ◽  
Henri J. L. van der Heiden ◽  
Roel Luppes
Keyword(s):  
Free Surface ◽  
Moving Objects ◽  
Cfd Simulation ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Adaptive Refinement ◽  
Efficiency Gain ◽  
Grid Refinement ◽  
Wave Impact ◽  
Area Of Interest

In many (wave) impact problems the area of interest does not change in time and is readily pointed out by hand, allowing for a one-time design of an efficient computational grid. However, for a large number of other applications, e.g. involving violent free-surface motion or moving objects, a reasonable efficiency gain can only be obtained by means of time-adaptive refinement of the grid. In previous studies a fixed, block-based Cartesian local grid refinement method was developed and implemented in the CFD simulation tool ComFLOW [1], a VOF-based Navier-Stokes solver on Cartesian grids with cut-cell discretization of the geometry. Special attention was paid to the interface discretization in cut-cells as well as the fluid displacement algorithm across refinement boundaries. The method was successfully applied to a range of offshore applications, including for example wave-impact on a semi-submersible (figure 1)and sloshing in a moonpool. In the present paper we present the first results of our attempts to extend the method to support adaptive refinement.

scholarly journals Laminar free-surface flow into a vertical cylinder

1975 ◽  
Vol 3 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Thomas G. Smith ◽  
J.O. Wilkes
Keyword(s):  
Free Surface ◽  
Vertical Cylinder ◽  
Free Surface Flow ◽  
Surface Flow

Free-Surface Flow Simulations With Interactively Moving Bodies

2017 ◽  
Author(s):  
Arthur E. P. Veldman ◽  
Henk Seubers ◽  
Peter van der Plas ◽  
Joop Helder
Keyword(s):  
Free Surface ◽  
Free Fall ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Numerical Solution Method ◽  
Flow Simulations ◽  
Floating Object ◽  
Offshore Industry ◽  
Floating Objects ◽  
Moving Bodies

The simulation of free-surface flow around moored or floating objects faces a series of challenges, concerning the flow modelling and the numerical solution method. One of the challenges is the simulation of objects whose dynamics is determined by a two-way interaction with the incoming waves. The ‘traditional’ way of numerically coupling the flow dynamics with the dynamics of a floating object becomes unstable (or requires severe underrelaxation) when the added mass is larger than the mass of the object. To deal with this two-way interaction, a more simultaneous type of numerical coupling is being developed. The paper will focus on this issue. To demonstrate the quasi-simultaneous method, a number of simulation results for engineering applications from the offshore industry will be presented, such as the motion of a moored TLP platform in extreme waves, and a free-fall life boat dropping into wavy water.

Sign in / Sign up

Export Citation Format

Share Document